Facebook today announced a new plugin called Shared Activity, which lists a user’s activities published from a given app to Facebook, including Open Graph activities, Like button stories, and comment plugin activities. The whole point is to let Facebook users control the activity they share on the social network from a given app, without having to leave that app and go to Facebook to manage it.

It’s meant as a simple way for developers to offer user controls without having to actually code them into their app. Facebook users can then set the default audience (public, friends, and so on) for activity shared from the app. The plugin does not control privacy settings within an app, as developers are still responsible for that part.

It also works retrospectively: users can change settings for stories previously published to Facebook, including selecting an audience or removing it altogether. I would argue that’s the best part, as Facebook users often become frustrated when they finally realize an app has been sharing too little, or more likely, too much and to too many people.

Here’s how Facebook tries to put the new plugin into context for you:

For example, when an individual uses a music app, she could modify the privacy settings, through the plugin, for specific song listening activities, without needing to go back to Facebook to control what’s shown. Similarly, if a person, through a travel app, likes a restaurant or reviews a hotel, and decides that these activities should only be viewable to a select group on friends on Facebook, he can control this within the plugin as well.

Facebook is of course pitching the new plugin as another way for users to control their sharing on the service, in addition to what’s already available: App Settings, inline on Timeline, and the Activity Log. It’s certainly a great addition, but it will only be useful if and when developers choose to include it in their apps.